An experimental and one-dimensional modeling analysis of turbulent gas ejection in pre-chamber engines

[EN] Experimental results from a study on the evolution of gas jets ejected through the orifices of a pre-chamber in a heavy-duty optical engine are presented. The work examines conditions without fuel inside the main-chamber, which helps to describe the dynamics of the ejected gas jets without the interference of subsequent combustion in the main-chamber. Experimental diagnostics consist of high-speed visible intensified imaging and low-speed infrared imaging. Additionally a one-dimensional gas jet model is used to characterize the spatial distribution of the ejected flow, including parameters such as tip penetration, which are then validated based on experimental results. Different stages in the ejection of pre-chamber jets are identified, with chemical activity restricted to a maximum distance of 5 to 10 orifice diameters downstream of the orifice as indicated by the recorded visible radiation. Sensitivity of cycle-to-cycle variations in pre-chamber jet development to the air-to-fuel ratio in the pre-chamber observed in the experiments is in most part attributed to the variations in the timing of combustion initiation in the pre-chamber. The influence of the ejection flow on the penetration of the gas jet on a cycle-tocycle basis is presented using the one-dimensional model. The one-dimensional model also indicates that the local flow exhibits highest sensitivity to operating conditions during the start of ejection until the timing when maximum flow is attained. Differences that exist during the decreasing mass-flow ejection time-period tend to smear out in part due to the transient slowdown of the ejection processThis research was sponsored by the U.S. Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE). Optical engine experiments were conducted at the Combustion Research Facility, Sandia National Laboratories, Livermore, CA. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. Jose M Garcia-Oliver acknowledges the support of the Generalitat Valenciana government in Spain through Grant Best/2019/176 for his scientific visit to the Combustion Research Facility. P. J. Martinez-Hernandiz is partly supported by an FPI contract (FPI-S2-19-21993) of the "Programa de Apoyo para la Investigacion y Desarrollo (PAID05-19)" of the Universitat Politecnica de ValenciaGarcía-Oliver, JM.; Niki, Y.; Rajasegar, R.; Novella Rosa, R.; Gómez-Soriano, J.; Martínez-Hernándiz, PJ.; Li, Z.... (2021). An experimental and one-dimensional modeling analysis of turbulent gas ejection in pre-chamber engines. Fuel. 299:1-15. https://doi.org/10.1016/j.fuel.2021.12086111529